De Gea denied Junior Hoilett, Marcus Olsson and Grant Hanley before the break, then repelled Morten Gamst Pedersen, who also had a goal disallowed in the second half.
"David de Gea made three fantastic saves to keep us in the game," said Ferguson.
"Although we had all the possession, we couldn't create the openings to get in front.
"Javier Hernandez hit the post and we had a penalty kick claim - I didn't think it was - so David has done his bit for the team.
"He has really grown in stature the boy. He was outstanding."